What is Orbital mechanics: Definition and 87 Discussions

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and law of universal gravitation. Orbital mechanics is a core discipline within space-mission design and control.
Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity, including both spacecraft and natural astronomical bodies such as star systems, planets, moons, and comets. Orbital mechanics focuses on spacecraft trajectories, including orbital maneuvers, orbital plane changes, and interplanetary transfers, and is used by mission planners to predict the results of propulsive maneuvers.
General relativity is a more exact theory than Newton's laws for calculating orbits, and is sometimes necessary for greater accuracy or in high-gravity situations (e.g. orbits near the Sun).

View More On Wikipedia.org
Recent contents Top users
  1. 2

    How can you tell what kind of orbit a body will have?

    Is there a way of telling whether the orbit of a body around another, or rather of both around their centre of mass, will give the object in question a circular, elliptical, hyperbolic or parabolic orbit? Thank you!
  2. T

    Difference between orbital mechanics and astrodynamics ?

    Hello all. The title of this thread sums up my question - what is the difference between orbital mechanics and astrodynamics ? Or is there a difference at all ? I have sometimes seen different uses of the terms, for example, on many sites I see " astrodynamics or orbital mechanics is ... " ...
  3. MattRob

    How Do You Calculate the Correct Launch Window for an Inclined Orbit Around Io?

    Sooo, this is something I'm really happy I figured out, buuuut, I want to make sure it's correct. I guess the context doesn't really matter, so you can skip the slashed part if you like. Honestly I'm not sure what forum this belongs in (Mathematics? Topology? There's no "geometry" forum, heh)...
  4. PhysicsStudnt

    Best beginner's material on orbital mechanics

    Hello experts, I would be glad if anyone could help me find out some basic beginners materials on ORBITAL MECHANICS. I am looking for ones that would help me understand the practical and technical aspects of launching a satellite, maintaining it in an orbit, changing orbits, results of...
  5. J

    Circular Motion - Orbital Mechanics

    Homework Statement Question 1. If two objects were in the same orbit around a planet they would both have the same orbital velocity regardless of their mass. Using the equation given, explain why an object with twice the mass experiences the same orbital velocity. Homework Equations...
  6. AotrsCommander

    Help with orbital mechanics for an unusual alien planet

    I wonder if I might pick the brains of the forum's experts? I am embarking on creating a new gaming campaign world, something I've wanted to do for years but never quite manged: an entirely alien world (i.e. not populated by humans or the like), yet with the same sort of technology as you'd...
  7. D

    Orbital mechanics - falling body

    Hello, my question id the following: when using Tsiolkovsky's equations to determine the velocity of a body after certain period of time, when the engine of a (space)craft is running, life is simple. But how do you calculate the falling rate of an object that is constantly falling, and then...
  8. D

    MHB State Matrix Derivation for Orbital Mechanics

    Has anyone seen the derivation of \(\ddot{\mathbf{r}} = -\frac{\mu}{r^3}\mathbf{r}\) into state matrix form? If so, can they provide a link?
  9. D

    Planetary rendezvous orbital mechanics

    Earth to Venus Hohmann transfer alignment time. Earth is at periapsis and Venus is at 190 degrees at ##t = 0##. For a Hohmann transfer, Venus must be lagging Earth by ##36.0298## degrees. I am trying to find the time it takes for the planets to align from their current positions. Is...
  10. D

    Simplifying total energy equation orbital mechanics

    I am trying to show that $$ \frac{\Delta v}{v_{c_1}} = \frac{1}{\sqrt{R}} - \frac{\sqrt{2}(1 - R)}{\sqrt{R(1+R)}} - 1 $$ where ##R=r_2/r_1##. ##r_1## is the radius of the circular orbit 1 and ##r_2## is the radius of the circular orbit 2. Similarly, ##v_{c_1}## is the velcotiy of the circular...
  11. D

    Orbital mechanics terminal velocity vectors

    For a given space triangle, derive expressions for the terminal velocity vectors ##\mathbf{v}_1## and ##\mathbf{v}_2## between points ##P_1## and ##P_2## in terms of the unit vectors ##\mathbf{u}_1##, ##\mathbf{u}_2## and ##\mathbf{u}_c##. I know that ##\sin\left(\frac{\alpha}{2}\right) =...
  12. M

    Orbital Mechanics Question - Speculative

    Hello, I am not a physicist or a physics student. I am an author, and I am trying to see if a Trinary star system I've dreamed up could work, and if so, what are the details as applies to my book. I hope someone can take the time to help me with this. The situation is this: I have imagined a...
  13. M

    How would Earth mass loss theoretically affect its orbital mechanics?

    Firstly, what happens to Earth's orbit around the sun should it gain or lose mass? I would instinctively guess that a less massive Earth would have less gravitational attraction to the sun, therefore widening the orbit. However, I understand that orbital mechanics can run counter-intuitively...
  14. W

    Understanding Orbital Mechanics & Elliptical Paths

    Hi. I was playing a video game where, in one level, you are in an orbit around an attractor. The game was 2D, so there's no inclination, etc. The game showed the projected path of the body around the attractor. When you used the games controls to thrust in a direction, it would show the...
  15. K

    Orbital mechanics: Accelrating takes you into a slower orbit?

    I'm confused by something very simple and stupid. When the mass of a satellite is tiny compared to the body being orbited, we can approximate orbital velocity as sqrt{(GM)/r} Now its obvious that as r gets larger, the orbital velocity drops. Higher orbits are slower orbits. A...
  16. J

    On orbital mechanics and the standard model

    Some Questions on Lagrange Points – According to Wicki, a Lagrange point is The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects (such as a satellite with respect...
  17. S

    Orbital mechanics- change of inclination

    Homework Statement I'm trying to solve this problem: What's the delta-v required to change a satellite's inclination from Earth's to Mars' plane? Where should the plane change be done for the minimum velocity change? ( Satellite's transfer will be done with Hohmann transfer orbit.)Homework...
  18. T

    Understanding Orbital Mechanics and the Concept of Sustained Circular Orbit

    When in orbit, a satellite is 'falling' with an accelerating velocity as per the simple gravity formula. Yet the Earth is 'dropping' away from the satellite at a constant rate since it is spherical. This means that the 'left over' value between those two rates should cause the satellite to...
  19. S

    How Do You Calculate Orbital Radius and Velocity for Different Orbital Periods?

    Homework Statement An impulse Engine, A, is located in Earth orbit with an orbital period of 9.6 hours. Another Impulse Engine, B, is located in Earth Orbit with an orbital period of 24.0 hours. a) What is the orbital radius and orbital velocity of IEA? b) What is the orbital radius and...
  20. S

    Where Can I Find Resources on Orbital Mechanics for Game Development?

    Not sure this is the right section for this question, but it seems the closest so... I'm part of a small team that's working on designing a scifi space-based realtime strategy (RTS) game. One of the things that we'd like to incorporate into the game is relatively realistic Newtonian physics...
  21. kreil

    Solve Orbital Mechanics Homework: Find Circular Orbit, Stability, Period

    Homework Statement I know how to do this problem, I'm just having trouble actually doing it. A particle moves in a force field described by, F(r)=-k(ar+1)\frac{e^{-ar}}{r^2} 1. Obtain the condition for a circular orbit of radius r0 2. Apply a perturbation to the circular orbit and find the...
  22. T

    Orbital Mechanics Specialization

    Hi, I'm a 4th year undergrad AE major and have been thinking about my career choices and graduate school choices a lot. Out of all the topics covered in my classes so far, I found orbital mechanics/ spacecraft mission design the most interesting. My question is, is it difficult to find...
  23. A

    Orbital Mechanics - effect of thrust on v, R, a

    Homework Statement A spacecraft orbits around the Earth at a tangential speed v and a radius R, in accordance with the equation a_{c} = \frac{v^{2}}{R} . a) If the spaceship's engines exert a force parallel to its instantaneous vector of motion, what is the effect on the quantities...
  24. M

    Net Gravitational Force on Object #1 with Distances A and B

    Homework Statement What is the magnitude of the gravitational force on object #1 as a result of object #2? Distance A = 0.383 m and distance B = 0.271 m. the diagram for the problem is here: http://students.physicsygoodness.com/user/1/graphics/image001.gif Homework Equations Fg=...
  25. C

    Help with Orbital Mechanics: First Post

    First post here, I'm a student in a BS in Space Studies program and I'm having a little trouble. I have R vectors = rI rJ rK V vectors= vI vJ vK ( I'm not putting in numbers to avoid someone doing my homework for me) I am having a hard time wraping my brain around getting...
  26. Philosophaie

    What equations are needed for calculating Keplerian orbital mechanics?

    I have some data about the elliptical orbits of the planets. I have a,e,i,ML,LP,N @ for a specific Julian Century, J2000. I need an equation check: w = LP - N EA = MA + e * sin(MA) * (1 + e * cos(MA)) x = a * (cos(EA) - e) y = a * sin(EA) * (1 - e^2)^0.5 r = (x^2 + y^2)^0.5 v =...
  27. S

    Missile Landing Radius Problem (Orbital mechanics)

    Homework Statement At time t=0, there is a missile at a height h directly above the perfectly round Earth moving tangential to the surface of Earth. What must be the maximum velocity of the missile at t=0 if it must land within radius r on Earth directly below its initial position by the time...
  28. F.Turner

    Why Does the Minimum Radius of Curvature Occur at the Apex in Parabolic Motion?

    Homework Statement A projectile in uniform gravitational field g=-g*j\hat{} with initial location x(t=0)=_{}xo, y(0)=_{}yo show explicitly that the minimum value of radius of curvature \partial of the resulting parabolic trajectory occurs at the apex and equal to (^{}vox)^2/g Homework...
  29. T

    MATLAB Matlab 2-D Simulation for TLI (Trans Lunar Injection) Basic Orbital Mechanics

    Matlab 2-D Simulation for TLI (Trans Lunar Injection) "Basic Orbital Mechanics" Hi Everyone, I have been assigned a project in which I am to program in MATLAB the solution to the 3-body problem, but in 2-D with a couple assumptions. 1) Earth and Moon are stationary. 2) Mass of spaceship...
  30. 1

    Do Orbital Inclinations Affect Hohmann Transfer Efficiency?

    My first post on this site, been reading for a while but joined up today so please bear with me :) I've got an assignment for my University orbital mechanics course. I couldn't find the place in the 'Homework' section, so i thought here would be ok. I've got a few pretty simple...
  31. S

    Is the Root 2 Relationship Valid for Orbital Mechanics on the Moon?

    I had thought that for an object in a simple circular orbit, the escape velocity would be root 2 times it's orbital speed. And that this should approximately apply for the Moon too. However Wikipedia here http://en.wikipedia.org/wiki/Moon gives the moon's escape velocity as 2.38 km/sec...
  32. M

    How to Calculate Orbital Approach and Docking in the Presence of a Gravity Well?

    This is not a homework problem. I want to learn how to perform this kind of “approach” calculation on my own. So I’m not interested in someone solving this particular problem, with these specific values, for me. What I want to know is what equations to use, and how to apply them, so that in the...
  33. E

    Apparent contradiction with orbital mechanics

    Consider a two body system for simplicity: M1 << M2. M1 is in a circular orbit about M2. The tangential speed of M1 is inversely proportional to its distance from the center of M2. However, in order to move to a lower orbit, or to de-orbit completely, M1 must lose tangential speed (in the...
  34. B

    Orbital Mechanics: NASA Launching Probes & GR/SR Considerations

    Hi. I was wondering how GR and/or SR is taken into account when the people over at NASA launch probes to comets, or any of the planets? I know GPS uses GR and SR and I've read a bit about that. But do they need to take into account GR/SR when planning missions or is the Newtonian limit good...
  35. DaveC426913

    Juggling and orbital mechanics

    This is really cool. [PLAIN]"[MEDIA=youtube[/URL] I notice the balls change speeds proportionate to their height on the wall as they follow their elliptical paths. Does their speed follow Kepler's 2nd Law?
  36. BobG

    Looking for an Introductory Book on Orbital Mechanics?

    Is anyone familiar with "Satellite Orbits: Models, Methods, Applications" by Montenbruck and Gill? I'm looking for something that starts a little more basic, but builds up to a decent level. I have my own copy of Vallado's Fundamentals of Astrodynamics and Applications, but it's a little...
  37. check

    Interactive Orbital Mechanics Simulation with Joystick Control

    http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html One of the best programs for anyone interested in orbital mechanics of space flight or anyone who just wants to simulate a shuttle or Apollo flight with a joystick. :smile: I found this a couple of days ago and have downloaded about...
Back
Top